Oukitel U11 Plus

Volume up -> menu how to boot
select Fastboot (go there with volume_up, select with volume_down
run
fastboot oem unlock
phone: question to unlock bootloader?
press volume up
then the fastboot oem unlock runs and unlocks the bootloader
fastboot oem unlock
< waiting for device >
...
(bootloader) Start unlock flow
OKAY [ 42.465s]
finished. total time: 42.465s
phone does not react
power switch 10 seconds
Orange state
Your device has been unlocked and cant't be trusted
Your device will boot in 5 seconds
phone switches off
switch on again, press volume_up for boot menu
select fastboot
run
# fastboot flash recovery recovery.img
< waiting for device >
target reported max download size of 134217728 bytes
sending 'recovery' (13534 KB)...
OKAY [ 0.668s]
writing 'recovery'...
OKAY [ 0.333s]
finished. total time: 1.001s
phone does not react
power switch 10 seconds
press volume_up to get to TWRP
see this video how to change the TWRP language if you don't understand Russian and downloaded a default Russian version
https://www.youtube.com/watch?v=vxPeYJYsUYU
No is a good time to insert a micro SD card and backup all partitions in TWRP, especially the nvram
Phone is always rebooting into TWRP Recovery, no matter what reboot option you choose.
therefore we try to lock the bootloader again
reboot to bootloader, at the same time run
fastboot oem lock
question on the phone
lock bootloader?
confirm with volume_up
fastboot oem lock
< waiting for device >
...
(bootloader) Start lock flow
OKAY [ 7.943s]
finished. total time: 7.943s
10 seconds power button to switch off
reboot system
no warning State Orange
(
Wipe
Dalvik / ART Cache
Cache
)notwendig?
flash supersu from SD card
reboot
Where to find the OTA update file in Android 7?
here it was downloaded to /data/data/com.adups.fota/files/adupsfota/update.zip
How to uninstall superSU?
https://forum.xda-developers.com/showpost.php?p=63615067&postcount=2459
Links
https://www.androidweblog.com/root-oukitel-u11-plus-4g-install-twrp-recovery/
https://forum.xda-developers.com/android/general/oukitel-u11-plus-development-support-t3627905
K9 mail stops syncing after some time, as caldav seems to do.
It seems to help to deactivate battery optimisation
go to Settings - Battery - menu: battery optimization
select 'All apps'
tap on K-9 Mail, select 'Don't optimize'
confirm
now syncing should work all the time

THL 5000

rooting

Rooting works with baidu root, version 2.4.6 (at the moment available only in
Chinese). I tried framaroot and towelroot, none of them worked.
The root is permanent and stays after a reboot.
After rooting install SuperSU instead of the Chinese root Permission program.
Then you can remove all the Chinese programs (one of them displays Chinese ads
in the status bar).

The only solution that worked for me was installing the recovery.img by hand on
the phone itself. But a recent custom recovery is needed to install the custom
ROM, wipe the dalvik cache and other things.

# fastboot update Cyanogen-VX.zip
archive does not contain 'android-info.txt'
archive does not contain 'android-product.txt'
error: update package has no android-info.txt or android-product.txt

reboot to bootloader
adb reboot bootloader

when the phone has booted into fastboot unlock the bootloader (I don't know if
this is really necessary, please give feedback)fastboot oem unlock
and follow the instructions on the screen (so obviously it was locked before
and unlocking was successful)

connect to the phoneadb shell

become rootsu

Download the TWRP archive from the linked page on .... and extract the recovery.img).
Next get the recovery.img for TWRP to the phone.

On one of the pages I found on the net they useadb push recovery.img /destination-folder/
but for me this did not work, because when becoming root with su I could not read the contents of the folders where I could push the file to.

So the quick and easy way for me was to download the recovery.img from a server
after becoming rootwget http://my.server/recovery.img
This way I had the file in a directory that I could access.

Then write the recovery.img directly to the necessary device (you are root, you can write anywhere, but you should know what you are doing!)dd if=recovery.img of=/dev/recovery
If that is successful you just made it. Now you have installed TWRP.

reboot recovery

If everything worked you should get into the TWRP recovery you just installed.

Now you can flash the ROM that you have copied to your SD-card, wipe all necessary memories/caches and enjoy your new ROM.

Doogee DG310 Voyager2

Rooting works with baidu root, version 2.4.6 (at the moment available only in
Chinese). I tried framaroot, towelroot, rootgenius and others, none of them worked.
The root is permanent and stays after a reboot.
After rooting install SuperSU instead of the Chinese root Permission program.
Then you can remove all the Chinese programs (one of them displays Chinese ads
in the status bar).